Thank you both for your input! It has helped me conclude the following when comparing AV Lifemiles/TK M&S :

Looking at these 2 airlines/programs side by side: TK have the advantage in terms of routes(way more, and to every continent). Avianca on the other hand, the furthest destinations they have are London,Spain,LAX. So although *A redemptions on TK are HORRIBLE, they do offer enough routes on TK metal to make that less of an issue.

So i believe it will be worth the trouble to move over to M&S. Lifemiles a few times a year do a sale where you can get up to 337k miles for .0147/mile, so buying them just for *A redemptions could done instead of bothering with M&S. Lifemiles award redemptions have very low redemption costs.

Plus M&S status appears easier to retain(lasts 2 years and required miles to renew is about half).